In offshore oil load and discharge operations, there is a systematic risk of oil leakage to the sea from damage to single carcass submarine or floating oil suction and discharge hoses. As used herein, a “single carcass hose” is a hose construction comprising only one carcass layer. Leakage from a single carcass hose may occur from a precipitous hose failure or a failure that materializes over time. Hose failure may result from overpressure of the system, a puncture from outside, sudden tensile break of the hose body, defects in the manufacture, construction or design of the hose, etc. In a single carcass hose construction, hose failure results in immediate oil leakage to the environment surrounding the hose. Such leakage is highly undesirable for obvious environmental and economic reasons.
Because of the risk of failure inherent in single carcass hose construction, a “double carcass” hose construction has been proposed and developed by those in the industry. A double carcass hose construction utilizes an outer hose carcass confining an inner hose carcass as an added safeguard. The outer hose functions to hold any oil or fluid that leaks through the inner hose carcass for a certain designed period of time. In a typical double carcass construction, a hose includes a main pressure cord or carcass layer as a primary confinement and an outer, or auxiliary, pressure cord layer formed so as to sheathe the inner carcass. A buffering space is defined between the carcass layers to retain fluid that leaks from the inner carcass. In use, it is common to connect hoses end-to-end to form a hose line for transporting oil or other fluid under pressure. U.S. Pat. No. 5,244,016 discloses a hose representative of the state of the art double carcass construction.
A double carcass hose is generally produced and utilized in two different types: submarine or floating configurations, depending on the type of application and offshore oil load and discharge system. Submarine applications require that a hose extend in submerged fashion between two points whereas a floating application requires that the hose extend across the water surface. In either application, leakage from the hose results in the aforementioned undesirable consequences.
In order to minimize the damage resulting from an undetected leak, various leak detection systems have been proposed and adopted. Such systems generally employ leak detectors of various configurations, operable under varying principles, mounted at the nipple region of an underwater hose connection. U.S. Pat. No. 5,654,499 teaches a detector mounted to an end of a hose for detecting fluid upon contact between a sensing medium and the fluid. U.S. Pat. No. 4,465,105 teaches a pressure sensitive switch for detecting by means of measuring the pressure of leakage fluid between carcass layers. U.S. Pat. No. 5,714,681 discloses an electro-optical sensor that utilizes an infrared beam that senses fluid levels when the beam is deflected.
In general, in offshore oil transfer hose lines using double carcass hoses, there is a constant physical check of hose and leak detectors required because most leak detectors are mechanical devices. The existence of an oil leak must be manually or visually confirmed by checking each leak detector. Consequently, a constant monitoring of each hose line is required. Such monitoring activities may be done by the oil company itself or a contract service provider. The monitoring entity keeps records and files detailing monitoring activity and typically hand-writes such records “in-situ”. However, local conditions may make it difficult for the monitoring entity to annotate data observed. Operational conditions may further be such (e.g. high seas) that there is substantial danger to operational personnel and also a risk that incorrect data will be observed and collected by the monitoring agent.
Existing leak monitoring systems and devices, therefore, while working well under benign conditions, may fail to provide accurate monitored data under certain other conditions. The leak detection devices themselves may be electrically unsafe in that they have active or power components within the oil collection space, creating a fire or explosion risk. Secondly, the communication systems in existing systems provide, at times, unreliable communication between the sensing elements and remote receivers or visual observers. The positioning of the sensors may also be affected by the floating hose line torsion when deploying the hose line into the water. The sensors may also be positioned incorrectly during hose line segment assembly. Finally hose lines move as a result of seawater and weather conditions and such movement can cause sensor position change/failure, or cause erroneous data collection by the monitoring agent.
Additional deficiencies in existing art sensing systems are that they are relatively large, expensive to manufacture, cumbersome to deploy, and provide a less than satisfactory degree of reliability and flexibility. Available systems typically provide one means of communicating the leak status of a hose segment or coupling. Such systems may use a mechanical sensor that communicates visually, such as by means of a flashing LED to an on-site observer. Other systems may detect a leak and communicate by signal transmission to a remote receiver. In some applications the first, inspection based system may be preferable while in other applications a transmitter based communication may be preferable. No system affords a user the flexibility of alternatively deploying different communication devices at the preference or election of the user.
Accordingly, the industry is in need of a flexible leak detector and system that is reliable, safe, efficient, miniaturized, and cost effective to manufacture, deploy, and maintain. A desired system will accurately provide leak detection data despite rough operational conditions and minimize data collection and transmission failures. Ideally, the system will be capable of communicating the leak status within a hose reliably throughout a wide range of operational conditions.